There has long been interest in developing thermoplastic blends containing semi-crystalline and amorphous materials that exhibit chemical resistance and good mechanical property retention at high temperature. Many semi-crystalline polymer blends demonstrate excellent chemical resistance and are well known in the art. However, the addition of neat amorphous materials to obtain high temperature property retention is not as well known or documented in the literature. These polymer blends generally tend to be incompatible and difficult to compound without the addition of fillers or additives such as glass, talc or mica. When a compatible unfilled resin blend is desired, it is often necessary to add a small amount of another ingredient or compatibilizer to promote more thorough blending between the two polymers. The additional ingredient(s) may work by promoting bond formation between the diverse polymer molecules of each material. It is very difficult to determine what ingredient(s) may work since compatibilizers that are effective in one polymer blend system may not be effective in others; a great deal depends upon the chemistry and specific functionalities of the molecules being blended and their interaction.
The reason for blending polymers is to create compositions that are better at meeting a specific need than an individual polymer or a polymer blend known in the art. Accordingly, it is sometimes desired to combine a polymer with another in the hopes of creating a blend exhibiting the desired characteristics of both polymers. In the present invention, polyphenylene sulfide (PPS) demonstrates excellent chemical resistance and good thermal stability which may potentially be important for polymer blends desiring such characteristics. In addition, polyphenylene sulfones (PPSU) exhibit excellent mechanical property retention at high temperature. The combination of these material properties is highly desirable, however PPSU and PPS are incompatible and therefore material blends are very difficult to compound and make into commercial products. The PPSU/PPS blends tend to have a morphology with large regions or domains of the individual polymers rather than fine, well-dispersed domains. The large domains tend to produce a material with poor mechanical properties, e.g. injection molded parts having poor tensile properties.